In the packaging field it is useful to seal containers, particularly cartons, with pressure sensitive adhesive tape. Two common types of cartons are the display carton (also known as a telescopic design box) and the regular slotted carton (also known as a regular slotted container, or RSC). The display carton includes a lower tray portion, in which the contents of the carton are placed, and an upper closure portion that covers the tray portion. The tray portion and the closure portion are adapted to fit together, typically with the tray portion inside the closure portion, and to be sealed by adhering one or more pieces of tape across the lower leading and lower trailing edges.
The regular slotted carton is generally a rectangular parallelepiped, including an upright leading surface, upright trailing surface, two side surfaces, and matching top and bottom surfaces. The top and bottom surfaces each include a flap connected to each of the upper and lower edges of the leading and trailing surfaces, and a flap connected to the upper and lower edge of each of the side surfaces, which flaps are folded inwardly to close the carton. The flaps connected to the edges of the leading and trailing surfaces are typically folded inwardly first, and the flaps connected to the edges of the side walls folded second, which positions the side wall flaps in abutting relationship along the length of the top surface and the bottom surface. To seal the carton, a section of tape may be applied to the flaps along the interface therebetween to adhere them together. For simplicity, the upper surface of the carton will be understood to include the abutting flaps, and the flaps comprising the lower surface of the carton will be referred to as the lower surface. The upper and lower surfaces will also be referred to jointly as longitudinal surfaces herein.
Devices are known which will automatically seal the upper or lower surface of a carton with tape as the carton is being driven past the device. Exemplary of such devices U.S. Pat. No. 4,789,418 (Rayl). The '418 patent discloses an apparatus that includes a tape head for applying an L-clip of tape to the leading surface and the lower surface of a carton, as well as to the lower surface and trailing surface of the carton. An "L-clip" refers to a piece of tape that is adhered to a portion of the leading surface, across the leading edge, and to a longitudinal surface of a carton or other object, because the cross-sectional shape of the tape section resembles a capital "L". One or more L-clips may also be applied across the lower leading edge, the lower trailing edge, or the upper trailing edge, depending upon the apparatus that is used.
The tape applicator of the '418 patent includes an application roller that is initially located in the path of the object, and has one end of a continuous supply of adhesive tape disposed thereon. The adhesive side of the tape is presented for contact with the leading surface of the carton as the carton is urged against the application roller. After the application roller contacts the leading surface of the carton, the roller is pivoted away from the carton by a pneumatic cylinder to a position beneath and spaced from the bottom surface of the carton. A blade severs the tape, and a wipedown assembly including two buffing rollers presses the tape against the leading and bottom surfaces of the carton to ensure adhesion thereto. A similar process is followed to adhere an L-clip of tape to the lower trailing corner of the carton. The apparatus of the '418 patent also includes a stripper assembly designed to strip tape from a tape supply and to maintain tension of the tape during the application process, which assembly adds cost and complexity to the tape applying apparatus.
One design consideration that is important in the carton sealing field regards the impact force and the application force of the application member against the carton. The impact force is applied by the application roller when it initially contacts the leading surface of the carton, and must be controlled in order to prevent the roller from compressing, denting, or crushing the leading surface or the contents of the carton. The application force is applied by the application roller as it traverses the leading surface of the carton, and must also be controlled for the reasons previously mentioned. The control of impact and application forces is particularly important when the object to which the L-clip is being applied is thin-walled, underfilled, or otherwise susceptible of damage.
Other types of tape applicators are also known. For example, U.S. Pat. No. 4,238,269 (Deering, Jr.) discloses a C-clip applicator, meaning that the apparatus applies a continuous length of pressure sensitive adhesive tape to a portion of the leading surface of a carton, across the top surface of the carton to seal the abutting flaps together, and to a portion of the trailing surface of the carton. As with the L-clip applicator, the C-clip applicator is so named because the cross-sectional view of the segment of tape used to seal the carton resembles the letter "C".
One feature of the apparatus of the '269 patent is the application of a uniform force by the applying roller against the leading surface of the carton being sealed. The application member is adapted for movement generally linearly in response to the application of force thereto by a carton. The '269 application member was therefore an improvement over previously designed application members that pivot about a fixed axis, due to the increasing compressive forces applied by a pivoting application arm to the corner of the carton being sealed.
While having its own utility, the apparatus of the '269 patent is directed to a C-clip applicator rather than an L-clip applicator, and it therefore addresses a distinct problem. For example, a C-clip applicator is not required to sever a section of tape at a point intermediate the longitudinal surface of the carton. Furthermore, although the application member of the '269 patent applied a low uniform force to the leading surface of a carton, it would be even more desirable to eliminate the application force completely. It is therefore desirable to provide an simple and inexpensive apparatus for applying an L-clip of pressure sensitive adhesive tape to a leading edge of an object while eliminating the application forces applied by the application member to the object.